Body parts of the slain dissident Saudi journalist Jamal Khashoggi were burned to ashes in an oven built to generate over 1000°C of heat inside the Saudi consul general’s home in Istanbul, a new report says.

According to a documentary aired by Al Jazeera Arabic Sunday night, Turkish authorities monitored the burning of the outdoor furnace as bags believed to be carrying the body parts were transferred to the premises.

A worker who constructed the furnace told Al Jazeera that the gas-powered oven was built according to specifications from the Saudi consul, including that the furnace should be deep and withstand temperatures above 1000 degrees Celsius - hot enough to melt metal.

Turkish authorities found that big chunks of meat were also cooked in the oven after the killing a few hundred meters away in order to cover up the cremation of the journalist’s body.

The documentary was based on interviews with some friends of Khashoggi, his fiance, Turkish friends close to the journalist, as well as with former political, media and security officials, the broadcaster said.

Turkish investigators also found traces of Khashoggi's blood on the walls of the Saudi consul's office after removing the paint that the assassination team had applied after killing the Washington Post columnist.

Khashoggi, a prominent critic of the Saudi crown prince and a US resident, disappeared on October 2 after visiting the Saudi consulate in Istanbul to obtain documentation for his forthcoming marriage.

Saudi Arabia initially claimed that he had left the consulate alive, but weeks later it had to admit that Khashoggi had been killed inside the diplomatic mission by a group of rogue operatives.

Turkish authorities believe that a 15-person “hit squad” was sent from Saudi Arabia to Istanbul to kill the 61-year-old journo.

Turkish President Recep Tayyip Erdogan has said the order to slay Khashoggi had been issued from “the highest levels” of the Saudi government, suggesting that Saudi Crown Prince Mohammed bin Salman had ordered such a gruesome crime.

The CIA is said to have also concluded that bin Salman had “probably ordered” the murder.

According to a highly-classified CIA assessment seen by The Wall Street Journal, the Saudi crown prince had sent at least 11 messages to his close aide Saud al-Qahtani in the hours surrounding the journalist’s killing.

A purported transcript of an audio recording of Khashoggi’s killing shared with CNN showed that his murder had been premeditated, unlike what Saudi officials initially claimed.

The transcript described the last painful moments of Khashoggi’s life, noting that his screams and gasps could be heard on the tape. It also identified the sounds of saw and cutting as the victim's body was dismembered.

Saudi Arabia has been facing international condemnation over the brutal murder.